This invention relates to printers, and more particularly to ink cartridges for printers.
Ink jet printers are a popular form of printer used with computers and similar applications involving document printing or graphics preparation. Typical ink jet printers, such as those manufactured by Hewlett Packard, have replaceable ink jet cartridges with built-in printheads. While such OEM ink jet cartridges are a convenient manner of supplying ink to such printers, the cartridges are necessarily expensive due to their complexity and the provision of printheads with the cartridges. Cartridges provided by printer manufacturers are typically not designed to be refilled when the ink supply runs out. It is well known, however, that such cartridges have useful lives significantly longer than that provided by the initial supply of ink; therefore, a substantial effort has been directed to providing systems for refilling cartridges with ink. The need to provide ink refilling is especially acute in the case of color ink cartridges, because typically one color will run out of ink before the other colors are depleted.
Refilling ink cartridges with ink is not an easy task. First, some means must be provided to break open the cartridges, such as the ink cartridge opener described in my U.S. Pat. No. 5,546,830, the disclosure of which is herein incorporated by reference. Then, because the ink reservoirs are typically filled with foam, the ink refilling process is slow due to slow absorption of ink by the foam. Users typically do not have the patience to refill slowly, and this causes ink to overflow from the top and from the printhead. In addition, it is very common to accidentally inject air into the foam reservoir during refilling, causing air lock in the ink reservoir. Ink then cannot reach the printhead, and the printer fails.
One prior art solution is a xe2x80x9cClip-Inxe2x80x9d type refill system. The original ink cartridge is modified by removing all of the original ink reservoirs, such that only the printheads and the case are left. Removable ink reservoirs are supplied, so the user only has to change the ink reservoir assembly causing no mess. The disadvantage of this system is that it the user must be supplied with a pre-modified cartridge specially-adapted for use only with the removable ink reservoirs, and in practice, this system is nearly as costly as OEM printer cartridges.
Thus, there presently exists a need for a simple and inexpensive method of refilling printer ink cartridges that eliminates the problems of slow refilling and potential air lock problems.
The present invention provides a replacement top portion for a printer ink cartridge that is useable with the original bottom portion of the OEM cartridge. The replacement top portion has internal walls defining at least one ink tank. Drain and vent conduits are adapted and arranged to slowly replenish the ink reservoir(s) in the bottom portion and to automatically maintain a level of ink in the reservoir until the replenishment ink in the top portion is depleted.